1. Technical Field
The present disclosure relates to devices for interfacing with high frequency data transfer media and, more particularly, to wire stabilizers, such as those that are used when installing a communication plug on an Unshielded Twisted Pair (“UTP”) media, that advantageously compensate for and reduce electrical noise.
2. Background Art
In data transmission, the signal originally transmitted through the data transfer media is not necessarily the signal received. The received signal will consist of the original signal after being modified by various distortions and additional unwanted signals that affect the original signal between transmission and reception. These distortions and unwanted signals are commonly collectively referred to as “electrical noise,” or simply “noise.” Noise is a primary limiting factor in the performance of a communication system. Many problems may arise from the existence of noise in connection with data transmissions, such as data errors, system malfunctions and/or loss of the intended signals.
The transmission of data, by itself, generally causes unwanted noise. Such internally generated noise arises from electromagnetic energy that is induced by the electrical energy in the individual signal-carrying lines within the data transfer media and/or data transfer connecting devices, such electromagnetic energy radiating onto or toward adjacent lines in the same media or device. This cross coupling of electromagnetic energy (i.e., electromagnetic interference or EMI) from a “source” line to a “victim” line is generally referred to as “crosstalk.”
Most data transfer media consist of multiple pairs of lines bundled together. Communication systems typically incorporate many such media and connectors for data transfer. Thus, there inherently exists an opportunity for significant crosstalk interference.
Crosstalk can be categorized in one of two forms. Near end crosstalk, commonly referred to as NEXT, arises from the effects of near field capacitive (electrostatic) and inductive (magnetic) coupling between source and victim electrical transmissions. NEXT increases the additive noise at the receiver and therefore degrades the signal to noise ratio (SNR). NEXT is generally the most significant form of crosstalk because the high-energy signal from an adjacent line can induce relatively significant crosstalk into the primary signal. The other form of crosstalk is far end crosstalk, or FEXT, which arises due to capacitive and inductive coupling between the source and victim electrical devices at the far end (or opposite end) of the transmission path. FEXT is typically less of an issue because the far end interfering signal is attenuated as it traverses the loop.
Unshielded Twisted Pair cable or UTP is a popular and widely used type of data transfer media. UTP is a very flexible, low cost media, and can be used for either voice or data communications. In fact, UTP is rapidly becoming the de facto standard for Local Area Networks (“LANs”) and other in-building voice and data communications applications. The wide acceptance and use of UTP for data and voice transmission is primarily due to the large installed base, low cost and ease of new installation. Another important feature of UTP is that it can be used for varied applications, such as for Ethernet, Token Ring, FDDI, ATM, EIA-232, ISDN, analog telephone (POTS), and other types of communication. This flexibility allows the same type of cable/system components (such as data jacks, plugs, cross-patch panels, and patch cables) to be used for an entire building, unlike shielded twisted pair media (“STP”).
There are typically four pairs of copper wires that are used, with each pair forming a twisted pair. The four pairs are used in horizontal cabling as well as for patch cabling or patch cordage. Patch cordage in terms of this disclosure is any unspecified length of UTP cable that is assembled by pressure crimping onto a RJ45 plug.
At present, UTP is being used for systems having increasingly higher data rates. Since demands on networks using UTP systems (e.g., 100 Mbit/s and 1200 Mbit/s transmission rates) have increased, it has become necessary to develop industry standards for higher system bandwidth performance. As the speeds have increased, so too has the noise. Systems and installations that began as simple analog telephone service and low speed network systems have now become high speed data systems. In particular, the data systems in the past used standard plug to cable assembly technique, which achieved reasonable Near-end Crosstalk (NEXT) and Far-end crosstalk (FEXT) noise levels and noise variability. The standard plug to cable assembly methods were used for the ANSI/TIA/EIA 568A “Commercial Building Telecommunications Cabling Standards” category 5 patch cords.
The ANSI/TIA/EIA 568A standard defines electrical performance for systems that utilize the 1 to 100 MHz frequency bandwidth range. Exemplary data systems that utilize the 1-100 MHz frequency bandwidth range include IEEE Token Ring, Ethernet10Base-T and 100Base-T. EIA/TIA-568 and the subsequent TSB-36 standards define five categories, as shown in the following Table, for quantifying the quality of the cable (for example, only Categories 3, 4, and 5 are considered “datagrade UTP”).
TABLECharacteristicspecified upCategoryto (MHz)Various Uses1NoneAlarm systems and other non-criticalapplications2NoneVoice, EIA-232, and other low speed data31610BASE-T Ethernet, 4-Mbits/s Token Ring,100BASE-T4, 100VG-AnyLAN, basic rateISDN. Generally the minimum standard fornew installations.42016-Mbits/s Token Ring. Not widely used.5100 TP-PMD, SONet, OC-3 (ATM),100BASE-TX. The most popular for newdata installations.
Underwriter's Laboratory defines a level-based system, which has minor differences relative to the EIA/TIA-568's category system. For example, UL requires the characteristics to be measured at various temperatures. However, generally (for example), UL Level V (Roman numerals are used) is the same as EIA's Category 5, and cables are usually marked with both EIA and UL rating designations.
Since the beginning of the ANSI/TIA/EIA 568A standard there has been no category 5 patch cord standard, but there has been a channel link standard. The channel link is a completely installed UTP cabling system that contains the patch cordage, connecting hardware and horizontal cables used for media connection of two or more network devices. The TIA/EIA is developing a patch cord standard as well as a plug level standard that will become requirements for development of category 5e (enhanced) and category 6 connecting hardwares.
Additionally, the EIA/TIA-568 standard specifies various electrical characteristics, including the maximum cross-talk (i.e., how much a signal in one pair interferes with the signal in another pair—through capacitive, inductive, and other types of coupling). Since this functional property is measured as how many decibels (dB) quieter the induced signal is than the original interfering signal, larger numbers reflect better performance.
Category 5 cabling systems generally provide adequate NEXT margins to allow for the high NEXT associated with use of present UTP system components. Demands for higher frequencies, more bandwidth and improved systems (e.g., Ethernet 1000Base-T) on UTP cabling, render existing systems and methods unacceptable. The TIA/EIA category 6 draft addendum related to new category 6 cabling standards illustrates heightened performance demands. For frequency bandwidths of 1 to 250 MHz, the draft addendum requires the minimum NEXT values at 100 MHz to be −39.9 dB and −33.1 dB at 250 MHz for a channel link, and −54 dB at 100 MHz and −46 dB at 250 MHz for connecting hardware. Increasing the bandwidth for new category 6 (i.e., from 1 to 100 MHz in category 5 to 1 to 250 MHz in category 6) increases the need to review opportunities for further reducing system noise.
By increasing the bandwidth from 1-100 MHz (cat 5) to 1-250 MHz (cat 6), tighter control of the components'noise variability is necessary. With the development of the new standards, the new plug noise variability will need to be better controlled than plugs that used old assembly methods.
Furthermore, the TIA/EIA Unshielded Twisted Pair Cabling task groups have developed a working draft for a UTP Connecting Hardware plug measurement parameter called NEXT de-embedding. The de-embedded NEXT procedure measures the pure NEXT and FEXT contributions of the plug and all other noise contributions are factored out of the final result. This method has become the de facto standard for RJ45 plug NEXT and FEXT characteristic measurement for plugs that are used to test connecting hardware performance. Plug de-embedded NEXT and FEXT variability was not an issue with category 5 connecting hardware or channel link systems, so upper and lower ranges were not specified. The TIA/EIA connecting hardware working groups have since realized that the plug de-embedded NEXT and FEXT must be controlled so the proper development of category 5e and category 6 connecting hardware/systems can become possible. The plug de-embedded NEXT and FEXT directly relates to the performance of the patch cordage and the connecting hardware that connects to it. Controlling the plug de-embedded NEXT and FEXT will enable control of the category 5, 5e and 6 NEXT performance. One method of category 5 connecting hardware crosstalk noise reduction and controlling is addressed in U.S. Pat. No. 5,618,185 to Aekins, the subject matter of which is hereby incorporated by reference.
The plug assembly crimping procedure heavily distorts the plug's de-embedded NEXT associated with patch cordage. This procedure is the final assembly method that forces the Insulation Displacement Contacts and the plug cable holding bar (also called strain relief) into their final resting positions. The plug cable holding bar is one of the main de-embedded NEXT disturbers since it distorts the wire pattern differently during the crimping stage.
In view of the increasing performance demands being placed on UTP systems, e.g., the implementation of category 6 standards, it would be beneficial to provide a device and/or methodology that is able to protect against wire distortion to reduce de-embedded NEXT and FEXT noises associated with patch cordage assembly.